AUTHOR=Li Xiaofang , Yin Jiaxuan , Wang Jingyu , Wu Ruixia , Li Shuaibing , Sun Weidong , Zhou Liang 

TITLE=High-efficiency solution-processed OLED based on trivalent europium complex by modifying the composition of the multiple-host system

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2022.965927

DOI=10.3389/fchem.2022.965927

ISSN=2296-2646

ABSTRACT=In this work, di-[4-(N,N-ditolylamino)-phenyl]cyclohexane (TAPC), 4,4’,4”-tri(9-carbazoyl)triphenylamine (TcTa), 9-(4-tert-Butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi) and 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene  (TmPyPB) were used to constitute multiple-hosts system and fabricate solution-processed organic light-emitting diodes (s-OLEDs) with europium complex Eu(DBM)3(Phen) (DBM=1,3-diphenylpropane-1,3-dione, Phen=1,10-phenonthroline) as emitter. To determine the optimal composition of multiple hosts system, a series of devices with different light-emitting layers (EMLs) were fabricated and compared. Experimental results revealed that removing TmPyPB out of multiple-hosts system greatly reduces the turn-on voltage while the addition of TcTa into multiple-hosts system helps to facilitate the transfer of holes from TAPC to Eu(DBM)3Phen molecules and thus increase the recombination probability of carriers on emitter molecules. Finally, high performance solution processed red OLED (turn-on voltage of 3.8 V) based on europium complex doped multiple-hosts system obtained the maximum current efficiency of 2.07 cd A-1, power efficiency of 1.54 lm W-1, external quantum efficiency of 1.2% and brightness of 945 cd m-2.